The invention has reference to an identity card comprising a sheet of synthetic material with a decoration pattern as is customary for papers of value and provided with information essential for the identification of the user or the object pertaining to the identity card.
Such identity cards are generally known nowadays. They are used for all kinds of purposes: card stating personal registration, card stating identity, credit card, cheque card or credit cheque, extract from an insurance policy, driver's licence, etc.
In those known cards the decoration pattern and the information considered to be essential for the identification of the user (personal data, portrait and/or signature, finger print) are printed, written or stamped on or adhered to the sheet of the synthetic material. This information may be protected by a laminate (adhered synthetic foil). Moreover the cards can be provided with a distinguishing relief print (embossing) or distinctive mark, e.g. in the shape of one or more magnetic strips or a postcode.
In practice it appears that the information on these known cards can be altered or replaced practically invisibly, for example by splitting up the cards into layers, cutting, using mechanical or chemical erasing methods, etc.
We have found that such "counterfeit techniques" are not possible without damaging or destroying the card beyond repair when the decoration pattern and the information essential for the identification of the user consist of sublimatable colouring agents dissolved in said synthetic material and bound to said synthetic material. The removal of information by extracting the colouring agents is not possible either without causing damage.